This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project seeks to understand the organization of auditory cortex in humans and the evolution of human-specific features of auditory cortex by comparing humans with chimpanzees (the animals most closely related to humans) and in macaque monkeys. We used neuroimaging and histological techniques to define higher-order auditory areas in humans, identify homologous areas in chimpanzees and macaques, and determine patterns of connectivity between auditory areas in the three species. During the reporting period, we built a comparative tissue collection to document the histology of primary and secondary auditory areas in macaques and chimpanzees. This involved sectioning two temporal lobes for each species, staining sets of sections for each species for Nissl, parvalbumin, and Wisteria florabunda agglutinin (WFA), and then scanning whole sections using the Center's Aperio slide scanning facility. This tissue collection is accessible for remote study by our colleagues at Vanderbilt and Nathan Kline. In addition, we stained sections of visual and auditory cortex with antibodies for glutamate transporters (VGLUT1, VGLUT2), These revealed the distribution of terminals originating in cells from the lateral geniculate and medial geniculate. This makes it possible to study the organization of thalamocortical connections in species that cannot be studied with invasive tracing techniques, specifically chimpanzees and humans.